In TypeScript, you can define basic types using a combination of built-in primitive types and custom types.

Here are some of the essential basic types:

Number

let amount: number = 20;

String

let course: string = 'Typescript';

Boolean

let isLoading: boolean = true;

let book;

function render(document: any) {
  console.log(document);
}

Array

let arrayOfNumber: number[] = [1, 2, 3];
let arrarOfString: string[] = ['apple', 'orange'];
let arrayOfAny = [];

Tupple

let tupples: [number, string] = [1, 'ayam'];

Enum

const enum Size {
  Small = 1,
  Medium,
  Large,
}

let mySize: Size = Size.Medium;
console.log(mySize); // 2

Object

let employee: {
  readonly id: number;
  name: string;
  retire: (date: Date) => void;
} = {
  id: 1,
  name: 'bayu',
  retire: (date: Date) => {
    console.log(date);
  },
};

Function

// without parameter
function calculateTax(): number {
  return 10;
}

// number parameter
function calculateTax2(income: number): number {
  if (income > 50000) return income * 2;
  return income * 1;
}

// number multiple parameter
function calculateTax3(income: number, taxYear: number): number {
  if (taxYear > 2022) return income * 2;
  return income * 1;
}
calculateTax3(10000, 2021);

// multiple & optional parameter
function calculateTax4(income: number, taxYear?: number): number {
  if ((taxYear || 2022) > 2022) return income * 2;
  return income * 1;
}
calculateTax4(10000);

// multiple, optional & default value parameter
function calculateTax5(income: number, taxYear = 2022): number {
  if (taxYear > 2022) return income * 2;
  return income * 1;
}
calculateTax5(10000);

Defining basic types in TypeScript is crucial for writing maintainable and error-free code. By specifying types explicitly, you can catch errors early in the development process and improve code readability. TypeScript provides a range of built-in primitive types, as well as the flexibility to create custom types, enabling you to create structured and organized applications.

Hope this helps!

How to define basic types in Typescript